Quadrapassel comes from the classic falling-block game, Tetris. The goal
of the game is to create complete horizontal lines of blocks, which will
disappear. The blocks come in seven different shapes made from four
blocks each: one straight, two L-shaped, one square, and two S-shaped.
The blocks fall from the top center of the screen in a random order. You
rotate the blocks and move them across the screen to drop them in
complete lines. You score by dropping blocks fast and completing lines.
As your score gets higher, you level up and the blocks fall faster.
